Priority is claimed herein with respect to German Patent Application Serial Nos. 101 12 499.6 filed on Mar. 15, 2001 and 101 57 266.2 filed on Nov. 22, 2001, the subject matter of which, along with the subject matter of each and every U.S. and foreign patent document mentioned herein, is incorporated herein by reference.
The invention relates to a resonator device, in particular a microwave resonator device, for testing a material quantity and especially a material flow in the tobacco-processing industry for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of the material or material flow. The resonator device is provided with at least one resonator housing and at least one opening in each resonator housing for the material or material flow to pass through.
The invention furthermore relates to a corresponding measuring device, especially a microwave measuring device, as well as a measuring system, in particular a microwave measuring system, for testing a material quantity and especially a material flow in the tobacco-processing industry for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of the material. Such a measuring device comprises at least one resonator housing, inside of which an electromagnetic field can be generated and which has at least one through opening for the material.
Finally, the invention relates to a method for testing a material for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of the material.
A corresponding resonator device or resonator housing for microwaves is known from German Patent No. 198 54 550 A1 commonly owned by the present assignee. This document discloses a resonator housing for the tobacco-processing industry, through which a rope of tobacco is moved and is subjected to microwaves for the purpose of detecting the weight and/or humidity level of the rope material. The purpose of this resonator housing is to improve the measuring accuracy and, if necessary, the measuring sensitivity when detecting the weight and/or humidity level of filler materials for ropes in the tobacco-processing industry. According to German Patent No. 198 54 550 A1, this is achieved by producing the housing at least in part from a material with a low expansion coefficient, so that with a corresponding fluctuation in the temperature, the housing essentially retains the same shape. It also improves the measuring accuracy if the resonator housing temperature is controlled to be at a constant value. Finally, it is advantageous according to the aforementioned reference if the interior housing walls are at least partially coated with a corrosion-resistant metal or consist of such a metal. The measuring accuracy for detecting the weight and/or humidity level for the aforementioned materials can be improved considerably in this way.
German Patent No. 101 00 664.0 also commonly owned by the present assignee, furthermore discloses a method for testing a production material or a material quantity primarily containing a production material, wherein the material is tested for the existence of a foreign substance. A microwave field is generated for this, the material is moved into the effective range of the microwave field and its influence on the microwave field is analyzed, wherein the actual values of a first and a second characteristic variable of the microwave field are measured simultaneously. A reliable value range is specified for these actual values and these are checked to determine whether the actual values are in the reliable range. A signal is generated if the actual values are outside of the reliable value range. For the purpose of this invention, the variable for a microwave field includes real variables of the generated microwave field, such as amplitude and phase, as well as variables of the components for guiding a microwave field, e.g. the resonance frequency and the band width of a resonator in which the microwave field propagates.
With the known measuring method, the goods to be measured are moved through the field of a resonator, wherein the dielectric properties of the goods to be measured change the field. By measuring the change in the resonance properties or the field, it is possible to determine the weight, density and humidity level as well as to detect foreign substances. However, it is difficult to detect very small foreign substances or to achieve a relatively exact local resolution. In particular the position of the foreign substance relative to the field orientation determines the measuring accuracy.
It is an object of the present invention to provide a resonator device, a measuring device and a measuring system, which increase the sensitivity of a method for determining whether a material flow contains a foreign substance and/or for detecting the weight, density and/or humidity level of the material flow or the material quantity.
Furthermore, it is an object of the present invention to increase the sensitivity of such a method and, in addition, provide means and a method for improving the accuracy and the local resolution of respective measurements.
The above and other objects are solved with a resonator device, in particular a microwave resonator for testing a material, in particular a material flow, in the tobacco-processing industry for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of the material or the material flow. The resonator device comprises a housing provided with an opening for the material quantity or the material flow to pass through, wherein the material can be transferred at least in part to a testing area, located in particular inside the resonator. At least one element that increases the energy density of electromagnetic waves is provided, wherein the energy density can be increased at least in a portion of the testing area.
As a result of this measure, a kind of bundling of the electromagnetic waves is possible in the testing area, which results in an increased flow of the respective waves, in particular microwaves, through the material to be checked or the region of the material flow to be checked. As a result, the sensitivity when measuring the weight, density and/or humidity level of the material flow and/or when testing for the existence of a foreign substance is increased, without the necessity of coupling additional energy into the resonator device. For the purpose of this invention, increasing or raising the energy density of electromagnetic waves in particular also means that these waves are bundled, focused, narrowed down or compacted. The electromagnetic waves preferably are microwaves. A material is advantageously tested with the resonator device according to the invention. The material advantageously is a material flow. For the purpose of this invention, the term testing region also encompasses the term measuring region.
The element preferably comprises a line resonator with at least one end face functioning as electrode. By using a line resonator, the waves coupled into the resonator can be bundled easily and effectively, wherein the waves or the respective field in particular exit the end face in the form of a beam.
It is advantageous if a coupling-in antenna and a coupling-out antenna are provided, which are arranged symmetrically inside the resonator. The antennas are furthermore arranged near a spot on the line resonator, where the field component that induces the coupling has a high amplitude, preferably a maximum.
A particularly good coupling of the waves coupled in and out of the element occurs if the element is preferably arranged inside a resonator cavity, at a distance to the walls delimiting the cavity.
A particularly effective method for testing the material flow is possible if the at least one end face is arranged near the material flow or the material quantity or the testing region. The size of the end face preferably is smaller than the region of the material flow, located inside a testing region in the resonator, wherein a cross-sectional surface that is essentially parallel to the end face is taken into consideration. The material flow, which in this case is a tobacco flow in the tobacco-processing industry that is advantageously wrapped with a wrapping material such as paper, refers to a cigarette rope having a circular diameter of approximately 6 to 10 mm. The size of the end face, which may be rectangular, is preferably smaller than {fraction (1/10)} of the area for the material flow to be projected against one wall of the resonator device. This refers, for example, to an area ratio as shown in FIG. 2, wherein the decisive area is the cross-sectional surface of the cigarette rope inside the cavity 7, which is shown in FIG. 2.
The line resonator preferably is a metal strip or a thin metal cube with an end face in the direction of the testing region. If at least one inside wall of the resonator housing preferably serves as an electrode, particularly as a backplate electrode to the end face, the electromagnetic wave field can be generated between the end face of the metal strip and the inside wall, so that a defined, narrowly limited measuring range is provided.
Two end faces are advantageously provided, which are directed toward the testing region. A particularly preferred embodiment of the resonator device has two end faces, wherein these are arranged opposite each other to allow the material flow to move through the space between the end faces. Such an embodiment of the resonator device permits a particularly even bundling of the waves, wherein an extremely high energy density is possible. The line resonator preferably is an open ring. In addition, the two end faces preferably are essentially parallel to each other, which further increases the homogeneity of the wave field.
Extremely reliable and exact measurements are possible if the one element consists at least in part of a material with low expansion coefficient, especially with respect to temperature. A long service life is ensured for the resonator device if the at least one element furthermore is coated with a corrosion-resistant material and in particular a metal and/or consists in part of such a material.
The invention further provides for a measuring device, in particular a microwave measuring device, for testing a material, especially a material flow in the tobacco-processing industry, for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of the material. The invention comprises at least one resonator housing, which is provided with at least one opening for the material to flow through and inside of which an electromagnetic field can be generated. The invention is modified in that the measuring device comprises at least two resonator housings, which respectively define one measuring range, wherein each electromagnetic field respectively comprises an electric field and the fields in the respective measuring regions are oriented in different spatial directions relative to each other. The electromagnetic field in this case is preferably a microwave field, comprising a stationary microwave field in the resonator housing. According to the invention, the different directions, relative to each other, of the electrical fields permit a more exact determination of foreign substances since foreign substances not detected with the one resonator housing can be detected with a high probability with the other resonator housing. In particular this refers to foreign substances having a geometric shape that is larger in one direction than in the other direction. Having different field directions relative to each other in space means, in particular, that these fields are distinguished by different angles relative to the conveying direction.
The measuring regions preferably are positioned successively in a conveying direction of the material flow, so that a separate evaluation of the respective measurements of the material quantity in the measuring regions can take place and so that the individual measuring regions are not influenced by the adjacent measuring region.
A particularly preferred embodiment of the present invention is obtained if the electrical fields are oriented essentially orthogonal to each other. For the purpose of this invention, orthogonal means perpendicular to each other.
If one electrical field is oriented essentially in the conveying direction of the material flow and one electrical field is oriented crosswise thereto, it is possible to take a measurement in the traditional manner, for example as described in German Patent No. 198 54 550 A1, as well as take a supplemental measurement crosswise to this direction.
For the purpose of this invention, field refers in particular to an electrical field. In the case of a dynamic field, the field intensity vector represents one field direction or orientation, as for a stationary electromagnetic wave.
If three resonator housings are provided, the measuring accuracy can be increased even further. For this, the third resonator housing is preferably designed so that the electrical field is positioned essentially orthogonal to the fields inside the other two resonator housings.
The measuring device according to the invention preferably comprises a resonator device that is designed or advantageously equipped according to the invention, as described in the above. A compact design for the measuring device is obtained if a single housing comprises at least two resonator housings.
According to a further aspect of the invention, there is provided a measuring system, particularly a microwave measuring system, for testing a material flow in the tobacco-processing industry for the existence of at least one foreign substance and/or for detecting the weight, density and/or humidity level of at least a section of the material flow. The measuring system is modified in that at least two measuring devices are provided for measuring the material flow in space, in different directions relative to each other. In this case, the measuring direction must be understood to be the direction of the field that is critical for the measurement, particularly the electrical field. For this, at least one measuring device is preferably designed such that a measuring in the conveying direction of the material flow is possible. German Patent No. 198 54 550 A1 shows in this connection, a corresponding measuring device that permits a measurement in the conveying direction of the material flow. One of the resonator devices according to the invention can be used, for example, as described in the above if at least one measuring device is designed to permit a measuring crosswise to the conveying direction of the material flow.
In a preferred embodiment of the invention, three measuring devices are advantageously provided, wherein the measuring devices are designed such that the material flow can be measured in three different spatial directions, relative to each other, in particular in essentially orthogonal directions. Very exact measurements and in particular measurements with a high local resolution are possible with a measuring system of this type. It is advantageous if the measuring device, which permits a measurement crosswise to the conveying direction, is one of the resonators according to the invention and described in the above.
According to yet another aspect of the invention, there is provided a method for testing a material quantity, in particular a material flow in the tobacco-processing industry, for the existence of a foreign substance and/or for detecting the weight, density and/or humidity of the material. For this, a first electromagnetic field is generated in a first resonator and a second electromagnetic field is generated in a second resonator, the material is moved through the first and the second field and a change in at least one characteristic of the electromagnetic field is measured.
The field intensity, the frequency or the phase, for example, can represent one characteristic of an electromagnetic field. In the case of a stationary wave field, the position of the antinodes or the nodes or the resonant frequency and the amplitude can furthermore represent one characteristic of an electromagnetic field, e.g. for a resonator.
The electrical fields are preferably oriented in different directions relative to each other. It must be assumed that the E field and the H field are oriented in different directions relative to each other. An even more exact analysis of the material flow based on the foreign substances or an even more exact detection of the density, humidity level and weight of the material flow is possible if a third resonator device is provided, which generates a third electromagnetic field. The material quantity is moved through this third field, which is oriented in a different direction relative to the first and second field, and the change in at least one characteristic of the third field is measured.
The electrical fields in the respective resonators are essentially positioned orthogonal to each other.
If the measured values are evaluated to generate an ejection signal, it is possible to separate out, for example, sections of the material flow from the further processing. As a result, it is possible to avoid the production of poorly filled cigarettes or cigarettes that are too dry or are composed of a foreign substance. The measured values from the resonators are preferably correlated, so that a very exact local resolution is possible. The rejection of conveyed material can be kept as low as possible with such an exact local resolution. Combining the measuring results from the different resonators thus increases the accuracy or the local resolution of the measurements.